Autologous fat injection for unilateral vocal fold paralysis.

This study evaluates the efficacy of autologous fat injection for medialization of the paralyzed vocal fold. In 21 patients with unilateral vocal fold paralysis, autologous abdominal fat was injected into the thyroarytenoid muscle to achieve medialization. All patients were followed up with serial videolaryngoscopy and voice evaluation. At 2 months' follow-up, the voice was judged to be excellent in 10 patients, slightly breathy but significantly better than the preoperative voice in 6 patients, and markedly breathy in 4 patients. At 3 to 4 months' follow-up, of the 10 patients with excellent results, 5 maintained an excellent voice, 3 had developed slight breathiness, and 1 had developed severe breathiness. Long-term (6 to 12 months) results were available in 11 patients, and all of them maintained the same voice quality that was noted during the 3 to 4 months' examination. Magnetic resonance imaging of the larynx was obtained in 7 patients at intervals ranging from 1 to 7 months and compared to the baseline scan obtained at 1 week postoperative to assess the amount of fat remaining in the muscle. The images showed fat volume to persist, but a decrease in the fat signal was observed over time. The results suggest that the duration of medialization with autologous fat is variable, but appears to last at least 2 to 3 months. This loss of volume after 3 months seems to be due to absorption of the fat and possibly muscle atrophy. Autologous fat injection is relatively safe and easy to perform, and is an ideal method of temporary vocal fold medialization in patients in whom return of vocal fold function is expected.

Autologous fat injection for vocal fold paralysis: long-term histologic evaluation.

Many techniques have been developed for medialization of the paralyzed vocal fold. The purpose of this study is to evaluate autologous fat as an alternative to alloplastic substances for use in vocal fold medialization. Eight dogs underwent left recurrent laryngeal nerve sectioning. Autologous fat was harvested, and the paralyzed vocal fold was medialized by injecting the fat into the thyroarytenoid muscle. The animals were divided into three groups for evaluation at 1, 3, and 6 months. Videolaryngoscopy was performed prior to sacrificing the animals. The larynges were sectioned coronally, and histologic studies were performed. The studies confirmed the preservation of viable fat at the injected site in all animals. Only a minimal inflammatory response was observed in the 1-month group. It would appear that fat injection is a viable alternative to Teflon injection and thyroplasty; it eliminates the need for alloplastic materials, does not appear to migrate, and does not require an open procedure.

The three bellies of the canine cricothyroid muscle.

The cricothyroid muscle is capable of multiple functions, including vocal cord elongation and adduction. In addition, the cricothyroid can lengthen the glottis as well as provide posture to the cricothyroid joint. The purpose of the present study is to demonstrate that the many functional capabilities of the cricothyroid are a reflection of the existence of separate bellies within the muscle. Microdissection revealed three distinct muscle bellies within the cricothyroid: rectus, oblique, and horizontal. These differ in fiber orientation (rectus 79 degrees, oblique 48 degrees, horizontal 7 degrees) and are separated by fascial planes. Histochemistry showed that these three bellies are composed of different percentages of slow twitch fibers (rectus 31.3%, oblique 43.3%, horizontal 39.6%). Finally, electromyography demonstrated differences in the electrical activity patterns of the three bellies. It is concluded that the cricothyroid muscle is composed of three distinct muscle bellies that probably play separate roles in the complex function of this muscle.